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    <script>

        var arr = [1, 3, 4, 2, 78, 54, 32];
        // 这个数组元素 和 的平均值

        // 思路:  求和 / 元素个数

        var sum = 0;
        for (var i = 0; i < arr.length; i++) {
            sum+=arr[i];
        }
        var arg = sum/arr.length;
        console.log(arg);
    </script>
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